Headlight glass or lens



Dem 255 19233 J. SQDERBERG HEADLIGHT GLASS OR LENE Filed Feb. 8.

FEEJL- FBE E.

INVENTOR Patented Dee. 25, 1123.

time

it rm.

JACOB SODER-BERG, OF PITTSBURGH; PENNSYLVANIA, ASSIGNOR TO PITTSBURGHPLATE GLASS COMPANY, A CORPORATION OF PENNSYLVANIA.

HEADLIGHT GLASS OR LENS.

Application filed- Eebruary 8, 1921.

To (ZZZ whom-it may concern."

Be it known. that LJAOOB I citizenof the United States, and a. residentof Pittsburgh, in the county of Allegheny and State of Pennsylvania,have made a- 443362, of even date herewith, being par-.

ticularly designed for automobile lamps. The present lens constitutes amodification of that. showninsaid applicationand difrefracting ferstherefrom in that the prisms are in part placed upon one side of theglass and in part upon the other side, instead of having all of theretracting elements-on the one side. The principle or theory of lightdistribution upon which the two lenses are constructed is similar andthe result secured substantially the same. The annular prisms on the oneside, tend to spread or bend the parallel rays so thatany upward glareis avoided. One embodiment of the invention is illustrated in theaccompanying drawings, wherein:

Figure 1 is a rear. elevation of thelens; Fig. 2 is a horizontal sectionon the line IIII of Fig. 1; and'Fig. 3 is a vertical section on theline.IIIIII- of Fig. 1.

It will be understood that the lens is designed tobe used in theusualway with the parabolic reflector which reflects the light.therefrom theoretically in substantially horizontal rays. However, dueto the fact that the filament of the lamp employed cannot beconcentratedatthe focus ofthe lens and extends forward and backwardof such focus, apart of the reflected light is more or less divergent from the axisoftheparabola, such divergence being greatest with respect to those rayswhich are reflected from those portions of the reflector nearest itscenter. into consideration in the design of the lens, the angles ofthehorizontal prisms nearest the center of the lens being accentuated togive a greater bending down eifect as com-' SODERBERG, a

This condition istaken Serial No. 443,361..

pared with the prisms adjacent the upper and lower edges of: the'lens.

The concentric diflusing ridges or prisms on-the rear face ofthe lensare so designed that the light will be spread laterally, that is in ahorizontal plane, to'just the amount necessary; to give the degree ofside light-- ing required. The horizontal prismson the front face of thelens arethen so designed that the diverging transmitted light is bentdownward, so that thegreater portion of thelight is thrownupon theroadway: at the desired distance forward of the lens, the light passingthrough the extreme upper edgeof the lens'beingbent downwardly so thatit is either horizontal or very nearly so; the'purpose being to fulfillthe requirements of the law for protectingthe occupants of approachingvehicles from glare due to up wardly. directed beams of light.

Referring ,now to the drawings, 1 isthe edge portion of the lens adaptedto be'fitted in the rim of the lamp; 2, 3, 4-, 5and Gare concentricridges or prisms-upon the rear face ofthe lens, and 7 te l? arehorizontal prisms ext-ending across'the front face of the lens. Theprisms 2vto 6 areof such angle that the parallel rays from the parabolic reflectorpassin'g therethrough are bent outwardly? from" the axisAof the reflector, the. amount'of the bending being determinedby theamount'of side lighting desired The prisms 7- to-17 bend this diverginglightdownwardly to the" desired extent with respect to the area upon theground infront of the lens-which it is de sired to. illuminate. Therayspassing throughthe upper portion of the lens must. of course,,bebentdownwardly more than those passing through the lower portion since therays fromthe upper'portion of the lens are bentupward by-th'e prisms onthe inside of the lens, while those on the: lower portion are bentdownwardly by such prisms. The angles of these horizontal prisms may bevaried in order to secure just the amount of downward bending de sired,and it will be understood that the illustration is not by any meansexact, the

angles of the prisms being greatly eXagcalled for if the light from thefilament of the'lamp were concentrated at the focus of the lens asheretofore referred to. The rays reflected from the central portion ofthe reflector, due to this condition,have a greater degree of divergencethan those from the outer portion of the reflector, so that the anglesof the central transverse prisms are made relatively heavier than wouldotherwise be the case. The angles of the other transverse prisms abovethe axis of the lens are so designed that very little, if any, of

the light transmitted passes above a hori-' zontal plane, theobjectionable glare which would otherwise occur, being thus avoided.

With respect to the angle of theprisms below the axis of the lens, thisis made to suit requirements and given just the desired amount ofillumination in the area'of roadway ahead of the car to which the lensis applied,.the angles of the prisms: on'the front of the lens and thoseon the back being carefully designed to avoid dark lines in the areailluminated and a uniform shading off of intensity from the center ofthe field of illumination to the outer edges thereof. The curved faceson the concentric prisms assist in securing this effect as the lightpassing therethrough is dilfused so that the light from the variousconcentric zones overlaps and blends. The transverse ridges also tend tobreak up any tendency to produce the appearance of concentric bands inthe field of illumination incident to the use of the concentric prisms.7 One oreat advantage of this lens is that the molds may be machined,therebeing no requirement for hand chipping such as is the case in themolds used for the formation of lenses in'which the prisms are notcontinuous. Such molds are not only expensive to makebecause' of thehand work required, but are correspondingly hard to re-surface after acertain amount of use. The face of the mold whichproducesthe concentricridges of the applicants lens may be machined in a lathe while theplunger which forms the transverse prisms may be machined in a planer ormilling machine. VV-hen the mold members need to be refinished, this canbe quickly and cheaply done following the method by which the moldmembers were originally machined. Because of this'possibility ofmachining the mold members may also be made of exceedingly hard, durablematerial, such as nichrome or stellite. This material may be machined orground but could not possibly be used in molds which require hand work,so that if desired, the applicant may-produce his molds from materialwhich may be used almost indefinitely before requiring re-surfacing andwhich will give a better surface on the glass than cast iron or othermolds of relatively soft material.

front side of'the lens. It is necessary'and i most desirable that thelight passing through the upper half of the lens be bent downwardly sothat the'uppermost rays are horizontal'or approximately so in order toavoid glare and avoid wasting a portion of the illumination, but this isnot so essential in the lower portion of the lens in which the lightisffor the most part bent downwardly by the annular prisms on the rearface of the lens. The degree of additional bending downward of the raysby 'the horizontal prisms is more or less a matter of discretion, suchrays being bent down little or. much, depending upon the lifghting' desired.' Similarly as to the variation in angle of the prisms in theupper half of the lens, the angle preferably increasing upward from thecenter as illustrated, for the reasons heretofore stated, but this isnot necessarily the case and the degree of angle may be considerablychanged. It is, however, quite important that the light transmittedthrough the lower part should be bent downwardly somewhat inorder togive the proper illumination immediately in front of the car. Also thatthat portion of the light transmitted just below the center of the lensshould be bent down more than that transmitted further down, as thelateral diver- V gence of'such light is. so great as to be of littleusefor side lighting when bent down sharply; however, this light is broughtclose enough to the car and to the center of the field of illuminationto be of value.

What I claim is: 7 r 1. In combination in a headlight lens or coverglass for use with a parabolic reflector,

a plate'of glass provided on one side with a series of complete annularprisms substantially symmetricalthroughout their circumference adaptedto bend substantially all of the parallel rays from the reflector awayfrom the axis thereof and provided on the other side witha plurality oftransversely extending prisms adapted to bend the rays downwardly, theangles of those transverse prisms nearest the center being reater thanthose above and below.

2; In combination in a headlight lens or cover glass for use with aparabolic reflector, a plate of glass provided on one side with a,

series of complete annular prisms substandownwardly, the angles of thosetransverse tially symmetrical throughout their circumprisms nearest thecenter being greater than ference adapted to bend substantially all ofthose below the center. 10 the parallel rays from the reflector away intestimony whereof, I have hereunto I from the axis thereof and providedon the subscribed my name this 2nd day of Feb other side With aplurality of transversely ruary, 1921. extending prisms adapted to bendthe rays JACOB SODERBERG.

